Variable high-frequency coil and/or tuning assembly



V Patented Dec. 16, 1952 UNITED STATES PATENT OFFICE VARIABLE HIGH-FREQUENCY COIL AND /OR TUNING ASSEMBLY Martin V. Kiebert, .l'r., Birmingham, Mich, and Alfred S. Backus, Passaic, N. 5., assignors to Mycalex Corporation of America, Clifton, N. J a corporation of New York Application July 6, 1951, Serial No. 235,454

Claims.

an improved high-frequency tank circuit which is space-saving and compact, stable, and insensitive to vibration though variable.

Another object of the invention is to provide an improved high-frequency tank circuit which tends to maintain optimum inductance-capacitance ratios over a relatively wide tuning range.

These objects and others ancillary thereto are attained by fixing an inductance coil upon a tube of molded insulating material which is adapted to rotate with respect to the surrounding tube, the internal core carrying an electrical conductor which is constructed so as to vary the inductance of the coil upon rotation of the core with respect to the coil or tube.

Suitable means for mounting or fixing the device on a chassis or control panel are also provided.

The insulating material of which the coilholding tube and internal core are constructed is preferably a glass-bonded mica product such as that sold under the trade name of Mycalex. Other insulating materials, preferably with high dielectric strengths and low power factors, may be employed. Titanates of barium, strontium, etc. may be added to the insulating material to increase its dielectric constant.

Ordinarily, the distributed capacitance of the coil itself can be utilized to furnish the capacitance for a high-frequency tank circuit. The coils can beat least partially embedded in the tube or sleeve which is made of an insulating material, such as Mycalex, which has a high dielectric constant so as to increase the distributed capacitance. In addition, condenser elements may be provided on the sleeve, which elements are so situated and constructed that rotation of the core changes the capacitance in such a way that maximum capacitance is obtained at the same time as maximum inductance and vice versa, whereby a greater range of resonance is obtained as well as a more desirable ratio of inductance to capacitance over the tuning range.

The novel features characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of opside.

eration, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which: Figure l is a side view (greatly enlarged) of one form of the device of the invention,

Figure 2 is a cross-sectional view of the device of Figure 1,

Figure 3 is a top view of a modified form of the device,

Figure 4 is a diagram illustrating the type of tank circuit obtained by the device of Figure 3.

The device comprises the tubular or sleeve number It] upon or within which the coil H is secured, the internal rotor or core and the attaching means 30.

The attaching means can take any convenient form. As shown it is made of metal and comprises a projecting end 3| to which the tube II is attached, an annular flange 32 which supports and is integrally sealed to the tube ID at one side and which also furnishes a bracketing surface for the attaching nut 33 at the opposite The end opposite the end 3| is threaded to receive the nut 33. An opening 35 extends through the member 30 to furnish a bearing surface for the shaft 2| of the rotatable core 20. A washer 36 may be included in the assembly.

The coil l is integrally molded into the sleeve member lfi and the axis of each of the mean individual turns |2, l3 and I4 of the coil II is at an acute angle for example) with respect to the axis of the sleeve I0 or rotor 20. As shown, about half of the diameter of wire on each of the turns |2, I3 and I4 is embedded in and firmly united to the tubular sleeve member Hi. The opening l5 in the tube I0 is cylindrical and smooth and when glass-bonded mica is employed as the tube material the inside dimensions can be molded Within close tolerances.

The rotor or core member 20 comprises the metal shaft 2| having the flange 22 and 23 at the end thereof adapted to securely clamp the molded insulating material of the body 25 of the rotor. Also molded into the rotor is the ring 24, the exposed surface of which is flush with the surface of the body 25. The body 25 is cylindrical and fits snugly within the cylindrical bore i5 of the tube Ill. The flanged end 22, 23 of the shaft 2| is spaced from the nearest coil turn |2 so that the said metallic shaft 2| does not influence the inductance of the coil II. In the position shown in Figure 2 the inductance of the device is at a minimum since the short-circuited 3 conducting ring 24 shorts out a certain portion of coil Rotation of the rotor 20 by 180 will give a maximum of inductance.

In the modified form of the device shown in Figure 3, the rotor 20, and attaching member 30 have thesame construction as in Figures 1 and 2, and like members refer to like parts in the various figures. The tubular stator element ID of Figure 3 is constructed somewhat differently. Connected adjacent to the beginning of the first turn I2 is the conductor 40, and a fiat capacitive element 4|. Connected to the end of the last turn I4 is a conductor element 42 and flat capacitive element 43. The efiect of the two capacitive elements 4| and 43 is to add capacitance to the distributed capacitance of the device. The capacitance is added in such a Way as to considerably increase the tuning range of the device, i. e., as the inductance is increased by rotation of the core member 20, the capacitance is also increased since the ring 24 approaches closer to the elements 4| and 43 and vice versa as the inductance is decreased the capacitance is decreased. The effect is to more than double the tuning range.

As an example of how the device works, if the three-turn coil as shown is approximately 1 centimeter in diameter and at an angle of approximately 45, and if glass-bonded mica is employed as the material of tube l and rotor 20, a frequency range of 215 to 228 megacycles is obtained without the aid of the added condenser elements 4| and 43. With the addition of the condenser elements 4| and 43, as shown, the frequency range is increased to from 205 to 245 megacycles.

It-isreadily apparent that the economies due to; this invention are greater than those due to previously made coils in that the coils made according to this invention permit greater space saving in tight-fitting and compact assemblies and are protected by their accurate construction from various outside mechanical influences. Since the coil H is firmly united to the tube l0. it is permanently positioned and electrically accurate. For example, the fixed coil II is not influenced by vibrations or accidental blows. Since the rotor 20 fits snugly Within the tube l0, it likewise is not influenced by vibration, etc.

We claim:

1. A combination tuning device consisting of an inductance comprising two terminals with at least one turn of a linear conducting material therebetween; a tubular sleeve of insulating material having a cylindrical opening therein, the turns of conducting material being embedded in the sleeve of insulating material with the axis of the mean coil turn being at an acute angle with respect to the axis of said tubular sleeve; a cylindrical rotor comprising a body member of insulating material having a ring of conducting material embedded therein with the axis of said ring at an acute angle with respect to the axis of the rotor, with means distant from the said ring adapted to rotate said rotor.

-2. The device of claim 1, in which the insulating material of said sleeve and said rotor consists of glass-bonded mica.

3. A combination tuning device consisting of an inductance comprising two terminals with at least one turn of a linear conducting material therebetween; a tubular sleeve of insulating material having a cylindrical opening therein, the turns of conducting material being embedded in the sleeve of insulating material with the axis of the mean coil turn being at an acute angle with respect to the axis of said tubular sleeve; a cylindrical rotor fitted within said cylindrical opening of said sleeve, said rotor comprising a body member of insulating material having a ring of conducting material embedded therein with the axis of said ring at an acute angle with respect to the axis of the rotor; a pair of capacitive elements fixed at opposite sides of said sleeve member and each connected to a differentone of said terminals.

4. The device of claim 3 in which the insulating material of said sleeve and said rotor consists of glass-bonded mica.

5. A combination tuning device consisting of an inductance comprising two terminals with at least one turn of a linear conducting material therebetween; a tubular sleeve of insulating material having a cylindrical opening therein, the turns of conducting material being embedded in the sleeve of insulating material with the axis of the mean coil turn being at an acute angle with respect to the axis of said tubular sleeve; a cylindrical rotor fitted within said cylindrical opening of said sleeve, said rotor comprising a body member of insulating material having a ring of conducting material embedded therein with the axis of said ring at an acute angle with respect to the axis of the rotor; a pair of capacitive elements fixed at opposite sides of said sleeve member and each connected to a different one of said terminals and with means insulated from and distant from said inductance member adapted to secure the device to a control panel.

MARTIN V. KIEBERT, JR.

ALFRED S. BACKUS.

REFERENCES CITED Ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

